1. Field of the Invention
The present invention is generally concerned with a torsional damper device of the kind comprising two coaxial parts disposed to rotate relative to one another about an idle relative angular configuration within predetermined limits of relative angular movement and circumferentially acting elastic means disposed between said parts along at least one circumference of the assembly so as to urge these parts elastically into their idle angular configuration.
The invention applies more particularly to torsional damper devices of the aforementioned type in which a first part comprises a hub flange and a second part comprises two guide rings disposed one on each side of said hub flange and linked together by spacers passing through said hub flange by means of circumferentially elongate oblong openings (notches or holes). These openings are delimited, as is known, by lateral flanks forming abutment members for limiting angular movement of the spacers and therefore of the hub flange.
The invention applies more particularly, but not exclusively, to damping torsional vibrations within a clutch disk, for automobile vehicles in particular. As is known, one of the coaxial parts, generally the hub flange, is then coupled, possibly with limited relative angular movement, to a hub mounted on a shaft known as the driven shaft, terminating at a gearbox, for example, whereas the other part, generally comprising the guide rings, carries at its periphery friction facings designed to be clamped selectively between two plates of a clutch.
As is known, the elastic means disposed between the two parts are more often than not in the form of helical springs of different stiffness disposed in the two coaxial parts so as to offer increasing resistance as the relative angular displacement between these parts increases.
2. Description of the Prior Art
A configuration of this kind is well known and is summarized, for example, in French Pat. Nos. 2 197 433 and 2 509 402. In known manner the friction members are disposed axially between the parts, for example in order to procure a "hysteresis" effect adapted to introduce differences in terms of behavior, for a given relative angular displacement, according to the direction in which this displacement is varying.
This arrangement of increasing stiffness elastic means is intended to procure appropriate filtering of torsional vibrations, both at low values of torque and when stopped, by virtue of the low stiffness elastic means, and at high values of torque, by virtue of the maximum stiffness elastic means.
However, it happens that in operation vibrations or sudden variations of the torque occur with an amplitude such that the aforementioned elastic means are incapable of absorbing them and preventing the occurrence of a sudden relative rotation between the two coaxial parts, which reaches the authorized limits of relative angular displacement. The spacers which link the guide rings then come sharply into abutment against the flanks of the associated openings in the hub flange, generating noise.
Apart from this disadvantageous noise, the abutting of the spacers against the associated flanks in this way causes mechanical damage to the damper device. Because of manufacturing tolerance in respect of the openings in the hub flange and the spacers, it is virtually inevitable that one of the spacers of the damper device will come into abutment engagement before the others. This results in highly localized wear and the risk of warping and eccentricity of the coaxial parts by virtue of the high values of off-center torque which arise transiently around the abutment area at the time of the impact.